Petrology of the mantle rocks from the Muslim Bagh Ophiolite,Balochistan,Pakistan

The muslim bagh ophiolite comprises two main blocks; the jang tor ghar massif and saplai tor ghar massif,and possesses an almost complete ophiolite sequence. a thick mantle section,comprising foliated peridotite,grades into transition zone dunite. the foliated peridotite is mainly harzburgite with minor dunite which occurs within harzburgite and contains podiform chromite deposits. the transition zone comprises residual dunite with impregnations of wehrlite/pyroxenite,and is formed by predominantly mantle processes at its base and crystal fractionation at the top. the chromite in the mantle dunites is mostly podiform and vein-like in shape. the mantle rocks are porphyritic,with harzburgite poor in modal clinopyroxene and dunite poor in pyroxene,indicating that the peridotites are residues after melt extraction. this residual nature is further confirmed by the higher cr # in spinel and mg # in orthopyroxene and olivine from the foliated peridotite,suggesting their derivation by higher degree of partial melting from a depleted mantle source. the petrology of peridotite and the presence of huge chromite deposits in muslim bagh dunites suggest that it is formed from processes within a supra-subduction zone tectonic setting.